Screening devices for, e.g., screening of light, heat, noise etc. from building openings, windows, doors with windows and like workpieces, exist in manually operated embodiments and as devices driven by, e.g., electricity via e.g., an electrical motor. The former exists in versions that allow for simple retrofitting in building openings, windows, doors etc., even by non-professionals, whereas the latter versions are usually more complex in their characteristics for the major part and require the efforts of a professional during installation. In particular, this is due to the fact that these constructions involve e.g. roller blinds provided with a roll-up mechanism which is electrically driven and which is mounted in a top box. The mechanism is usually driven by a main voltage, which is one of the reason for using a professional assembler but other reasons may often be installation of control mechanisms, wiring etc.
Various devices have been suggested in which battery-driven electrical motors have worked as the drive means. Thus, it has been suggested, cf. U.S. Pat. No. 5,517,094, to mount a drive means with batteries and an electrical motor on the top box of a Venetian blind screening device, the drive means being mounted as a separate unit on the outside of the top box.
Meanwhile, there has been a desire to create a device in which the electrical drive means is not retrofitted but integrated in the screening device itself so that a more compact construction may be achieved with a larger degree of aesthetics.
This is known from, e.g., WO 00/05478 in which an electrical motor and a battery have been integrated in a bottom bar of a screening device which may be controlled via a remote control and in which the screening device is lead in a parallel guiding arrangement via two cords or strings which extend from the top to the bottom of a window in such a manner that they are led through the bottom bar in which they cross.
Since the electrical drive means is integrated in the bottom bar, which moves up and down, the energy may necessarily be supplied by a battery placed in the bottom bar in order to present a practical energy supply.
By such screening devices and drive means, which may be driven by some kind of automatism, by electricity or other means, and which may potentially be operated via remote control, it will often be problematic to operate these manually if so desired. Thus, one case may be that of attempting to push, e.g., the roller blinds up where it will be necessary to at the same time drive the drive means whereby the roller blinds are usually driven, e.g. an electrical motor, a transmission mechanism etc., and this may be complicated and inconvenient in practice.
Furthermore, in some cases, such drive mechanism may be designed as a self-locking mechanism to prevent, e.g., a drive means for roller blinds from rolling downwards to dispense the blinds due to gravity or upwards to store the blinds due to spring power, whereby the roller blinds are rolled up when the drive means allows it. In these cases, it will not be possible to push the adjustment drive manually.
As mentioned, a drive means is known from WO 00/05478, according to which an electrical motor and a battery are integrated in the bottom bar of a screening device controlled via a remote control and according to which the screening device is led in a parallel guiding arrangement via two cords or strings extending from the top to the bottom of a window in such a manner that they are led through the bottom bar in which they cross. By this construction, one embodiment introduces a self-locking mechanism which is related to the drive means while at the same time allowing for manual operation by deactivating a clutch. However, this has not been elaborated upon in the publication.